1. Field of the Invention
The present invention generally relates to lighting systems. More particularly, the present invention relates to lighting systems for residential or commercial structures in which energy conservation and ease of upgrading existing lighting systems are major concerns.
2. Discussion of the Related Art
Central lighting control systems, as used in commercial buildings, automatically turn lights on and off based on time of day. Many lighting control systems have included motion sensors and light harvesting sensors, which provide additional control in turning lights on and off. Motion sensors are typically used in areas, such as hallways or storage rooms, in which people are occasionally present. Light harvesting sensors, typically used in exterior offices with windows, turn lights on and off based on the presence of ambient sun light. The additional control provided by motion sensors and light harvesting sensors is intended to improve energy efficiency.
Central lighting systems typically use hard-wired switch relays on lighting circuits that are located in a central control box.
Central lighting control based on time of day, motion, and ambient sunlight, are expensive to implement. First, they are expensive to install because each individual circuit line feeder must be wired back to a central system. In many cases, these lighting systems are retrofitted into existing buildings, which is extremely labor intensive and generally cost prohibitive, especially in large commercial office buildings. Further, related art central lighting control systems are restricted to on/off functionality, because they rely on the use of relays. As such, dimming control is generally not available in a central lighting control system.
Second, lighting control systems that utilize motion, light harvesting, and time of use controls generally need to provide a secondary signal, such as a low voltage control signal, via a control wire that is connected to each of the lighting fixtures' ballasts. For instance, if two or three fixtures are controlled by a light harvesting sensor, each of the fixtures will need to be wired in parallel to the sensor. Accordingly, an electrician has to run a control wire from light fixture to light fixture and then back to the sensor. If two or three fixtures are to be controlled by a motion sensor, the same holds true in that the electrician has to run a control wire from fixture to fixture and then back to the motion sensor. The running of a control wire to each fixture is very expensive, which prevents most enterprises from retrofitting their offices with more energy efficient lighting control systems.
What is needed is a lighting control system that can be installed with minimal invasive wiring to the lighting circuit and the individual ballasts, enables dimming control, and can take advantage of motion sensors and light harvesting sensors to improve energy efficiency.